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• ffplay won't with with more than 6 audio channels

  13 juin 2020, par Hiko Haieto

  I am trying to stream (raw) video and audio from a capture device as part of my home media setup (with my pc acting similarly to a receiver in a typical home theatre setup), but the biggest problem I haven't been able to get past is that I haven't been able to get ffplay to work with all 8 channels in 7.1 streams - two simply get dropped, despite it recognising 8 channel input or me specifying a 7.1 layout.

  



  I have been able to confirm that all 8 channels are present in the source by first using ffmpeg to save the output of a speaker test to a file and playing that back with both mplayer (which works) and ffplay (which doesn't). I might simply use mplayer if it weren't for the fact that piping output from ffmpeg adds too much latency for real-time use. I am using libSDL version 2.0.12 and ffplay 4.2.3, both of which are the latest at the time of writing and are ostensibly supposed to support 7.1 audio.

  



  Using output recorded from speaker-test -c 8, I am using the following to play it back in mplayer :

  



  mplayer -channels 8 -rawaudio channels=8 -format s16le -demuxer rawaudio speaker-test.pcm


  



  and the following to play it back in ffplay :

  



  ffplay -f s16le -ac 8 -af 'channelmap=channel_layout=7.1' speaker-test.pcm


  



  No matter what I try, ffplay is dropping the two side channels. Why might ffplay not be producing output for all 8 channels, and how might I fix it ?

  


• Why does the remainder of the video not appear in this FFMPEG complex filter graph ?

  10 janvier 2019, par Jonathan Gilbert

  I have a filter graph where I am trying to shift the first 18 seconds of a long video up by 60 pixels in each frame (the frame size is 1920x1040) without affecting the rest of the video. The graph definition looks like this :

  -filter_complex "[0:v] trim=start=0:duration=18 [pretitle];\
  
                   [0:v] trim=start=18,setpts=PTS-STARTPTS [remainder];\
  
                   color=color=black:size=1920x1040 [blank];\
  
                   [blank][pretitle] overlay=0:-60 [pretitle_shifted];\
  
                   [pretitle_shifted][remainder] concat [t];\
  
                   [t] ass=Subtitles.ass,fade=t=out:st=2608.6:d=2 [output]"
  
  -map [output] -map 0:1

  This filter graph runs without errors, but after the first 18 seconds, the video is just the subtitles on a black background. I can’t figure out why. :-(

• ffmpeg add text every second with enable between filter

  12 janvier 2023, par HUNG

  ffmpeg -y -i public/media/vid1.mp4 -vf "drawtext=text='1':x=w-tw-50:y=50:fontcolor=black:fontsize=380:enable='between(t,1,2)',drawtext=text='2':x=w-tw-50:y=50:fontcolor=black:fontsize=380:enable='between(t,0,1)'" -codec:a copy public/media/vid1-1.mp4


  


  I want to add a number every second in a video. I googled and the syntax should like the above. However, only the text within between(t,0,1) can be shown and the value is keeping shown for the whole video duration. But I expected it should only show one second.

  


  I expected between(t,1,2) can show the text from 00:00:01-00:00:02. However, it never show.